Heavy traffic makes its way north on Capital Boulevard on Monday in Raleigh. New apps for smartphones and other digital devices allow users to receive and enter real-time warnings about Triangle traffic jams. ssharpe@newsobserver.com

Heavy traffic makes its way north on Capital Boulevard on Monday in Raleigh. New apps for smartphones and other digital devices allow users to receive and enter real-time warnings about Triangle traffic jams. ssharpe@newsobserver.com

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When your Waze app is running, the GPS element in your smartphone broadcasts your location and travel speed. Somewhere in the Internet cloud, a clever algorithm combines other traffic info with this data from Waze users in the area – and then tells you how things are going, right now, on the road ahead.

The Waze map is sprinkled with smiley-face car icons that represent individual Waze users, with their nicknames (mine is “Road_Worrier”). You see how slowly the rush-hour traffic is moving, where the trouble spots are and what time you can expect to get to work.

Sometimes your phone utters a squawk and warns you to take the next exit.

“If I’m driving and I-40 is completely red and blocked, it says, ‘Try this alternate route,’ ” said Chris Boulton, 53, who commutes each day from Chapel Hill to Cary.

Along with this passive data feed from their telephone GPS signals, many drivers also share active alerts about what they see on the road: an accident, a dead animal, a police officer on the shoulder. It’s an updated version of the trucker spreading an alert with his CB radio, or the lone driver flashing her headlights to warn oncoming drivers about danger ahead.

Waze tells you this hazard is, say, half a mile ahead and then counts down the distance as you grow closer. You’re invited to confirm that it’s still there by tapping a thumbs-up button, or else click a link to say that it’s “not there” now.

Frank Bouknight responds when he can, with a tap of his thumb. But these alerts can be more of an annoyance than a help.

“That can be a distraction,” said Bouknight, 75, of North Raleigh. “There are times I don’t respond to that. I keep driving with both hands on the wheel. It depends on how attentive I’ve got to be to the traffic – that’s first, always.”

Predicting time

Waze and INRIX Traffic users say the apps are uncannily accurate in predicting what time you’ll reach your destination. These estimates sometimes are adjusted by a minute or two along the way, as traffic jams build up or melt away.

Before Burnett heads home in the afternoon from his employer’s office in Apex, he consults the INRIX map to see whether the I-440 Beltline is clear or whether it’ll be faster to drive a few miles out of the way, on I-540.

The state Department of Transportation uses a real-time feed from INRIX to produce its color-coded traffic maps, showing where the jams are. And in the early months of a three-year Beltline repair project, INRIX data is helping DOT gauge traffic delays that will affect Triangle commuters through the end of 2016.

The #BeltlineJam project has closed all but two lanes each way on a 3.5-mile section of the Interstate 440 Beltline in Southeast Raleigh, causing frequent backups for drivers approaching on I-40 from both directions. Each morning, INRIX measures travel times on I-40 from N.C. 42 in Johnston County to the I-40/I-440 Beltline split (11.2 miles) and to the I-440 Poole Road exit (14 miles).

These times are calculated every five minutes during rush hour, starting for cars leaving N.C. 42 at 6 a.m. and ending at 9:25 a.m. Then they’re compared to INRIX times from a comparable day one year ago – for example, the second Tuesday in May.

As traffic gets heavier, the delays get longer. At the peak of the morning rush, between 7:30 and 8 a.m., the squeezed I-440 traffic adds almost three minutes, on average, to the drive from N.C. 42 to the Beltline split.

DOT engineers are starting to learn how they can use this information to help drivers each day. Those #BeltlineJam delays are expected to be a lot worse starting in early 2015, when the lane closings move to the more heavily traveled I-40 section of the Beltline.

“As an industry, we are looking at how transportation management centers can use social media to do our jobs better,” said Kelly Wells, a traffic engineer at DOT’s transportation operations center in West Raleigh.

She and her co-workers watch freeway cameras, check updates from roadside traffic sensors and field accident reports from the Highway Patrol. Meanwhile, the INRIX feed turns cars and trucks into rolling traffic sensors, telling engineers and drivers about conditions on thousands of miles of roads where there are no cameras.

“We can see where there are incidents on I-95, even where we don’t have a camera,” Wells said. “You can’t see the road, but you can see where traffic is slowing down. And if something closes a lane, we can say, ‘Look, the traffic is backed up for 5 miles.’ ”

Commuters using these apps often learn about accidents and traffic jams before the troopers do, and long before the word gets out on Twitter and radio.

Privacy questions

But in sharing this personal travel information, drivers also are crossing another frontier in the Internet privacy realm. Your Waze account includes a record, with maps and timestamps, of every trip you’ve taken.

And as smart as this software usually is, the Road Worrier is happy to report that Waze can be stupid, too.

When heavy morning traffic backs up on N.C. 54 at a stoplight near I-40 in Durham County, Waze gets impatient. Rather than wait for the green light, I am advised to circle around the shopping center on the corner.

And when out-of-state friends are coming to visit our house in rural Orange County, Waze leads them astray. Failing to recognize that my cul-de-sac is accessible only from one road, Waze has sent drivers miles away into another subdivision that backs up against my neighborhood.

They ended up at the end of another cul-de-sac where they would have to travel the last hundred yards through the woods, on foot. That’s when they picked up the phone and called for directions.